I have just bought and installed beta 5.03.1 on Windows 10 and Windows 8.1. I have been thrashing it for 4 days solid, and I have not had one stability problem.

I have created sandboxes for my internet facing apps (IE, Firefox, & Chrome browsers and Outlook email client) and removable media devices. Everything works well. As documented on this website, Trusteer Rapport and Norton Identity Safe do not work in a sandbox, but that is due to technology constraints.

Sandboxie completes my 'Defence in Depth' strategy by plugging a security gap not covered by all my other security products.

One thought:
The nice graphic of a disk layout on this website that explains how Sandboxie works is by partitioning files into one area of disk may be good for non-technical users, but it is misleadingly overly simplistic for technical users. It was not until I persisted with a lot of digging, that I was able to confirm that Sandboxie provides sandboxed protection for files, disk devices, registry keys, processes, threads, driver objects, named pipes, mailbox objects, events, mutexs, semaphores, sections, and LPC ports. It may be a good idea to place a footnote under the simplistic graphic stating this.